The Prime Minister and his new deputy were all smiles as they vowed to work together for a brighter future. [>

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They hailed their Tory-Lib Dem coalition as a defining moment in British history, based on “hope and unity”. [>

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But the sober atmosphere soon descended into laughter when the PM was put on the spot over a dig he once made against Clegg. [>

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Two years ago, the Tory leader, 43, was asked what his favourite joke was and he replied simply: “Nick Clegg, at the moment.” [>

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There was laughter from the media scrum in the Downing Street gardens as red-faced Cameron was forced to confess to his deputy: “I’m afraid I did.” [>

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Clegg, also 43, pretended to storm away, saying: “I’m off,” only for Cameron to call out sheepishly: “Come back…” [>

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Pundits are already joking that they will have to decide where each will stand – just like I’m A Celeb hosts Ant & Dec. [>

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The duo’s wise-cracking was in stark contrast to the three TV debates in which they attacked each other and their policies. [>

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But the pair pledged to set aside party differences to make sure their new pact holds firm for the benefit of Britain. [>

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Cameron said his joke about Clegg underlined the hurdles they face in getting voters to accept the coalition. [>

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He said: “We are all going to have things we said thrown back at us. [>

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“And if it means swallowing some humble pie, and if it means eating some of your words, I cannot think of a more excellent diet in which to provide the country with good government.” [>

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He said their first priority was to begin confronting the colossal national debt. [>

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Telling voters their alliance was based around “freedom, fairness and responsibility”, the PM said: “Together, that job starts today.” [>

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But the scale of concessions the Tories made to win Lib Dem support became clear yesterday. [>

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It emerged workers will face Labour’s 1p National Insurance hike but firms will not. [>

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Cameron had claimed during the election campaign that Gordon Brown’s “jobs tax” would strangle the recovery. [>

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Middle-income earners will also lose out on inheritance and capital gains tax breaks. [>

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The two leaders, who earlier shook hands and shared back-slaps on the steps of Downing Street, said their pact had the “full backing” of their parties. [>

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Foreign Secretary William Hague said they had made big compromises, adding: “There are many things the Liberal Democrats have had to swallow that are very difficult for them, just as there are some things – like holding a [>

referendum on a new voting system – that are very difficult for the Conservative Party to accept. [>

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“That means, of course, there will be people in both parties who quietly wish it hadn’t happened.” [>

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The race to become Labour’s new leader kicked off yesterday as former Foreign Secretary David Miliband, 44, formally put his name forward. [>

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Bookies made him favourite as another front-runner, ex-Home Secretary Alan Johnson, 59, ruled himself out. [>

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Meanwhile, Tony Blair’s former spin chief Alastair Campbell said the first volume of his diaries will be published next month. [>